1. Field of the Invention
This invention relates to a wheel end disconnect system, or unit, for a vehicle, and more particularly, to such a system which includes a clutch shiftable between positions for connecting and disconnecting drive and driven components thereof to render selected wheels passive or power-driven.
2. Description of Related Art
This invention has particular application to four-wheel drive vehicles wherein the front wheels or the rear wheels are engaged to be driven by the drive train only as required. For purposes of discussion, the rear wheels will be treated as constantly driven, and the front wheels will be referred to as the set of wheels that are selectively engaged to be driven by the drive train. A transfer case coupled to the vehicle transmission has suitable gearing to be engaged or disengaged as needed. The engagement of the transfer case gearing selectively supplies power to the front drive train which will drive the front wheels. It is desirable to be able to engage the front wheels with the front drive train when the front drive train is under power and to disengage the wheels when the front drive train is idle. This disengagement of the front wheels from the drive train prevents forced rotation of the drive train as a result of the front wheels being driven as the vehicle is propelled.
It thus will be appreciated that in the example given, there are two positions in the drive train in which a connect/disconnect mechanism is required. For purposes of explanation, the invention will hereafter be discussed merely in relation to a wheel end unit, recognizing that such can be either for a front wheel or a rear wheel, depending upon which portion of the vehicle has primary drive function.
Generally in four-wheel drive vehicles where a connect/disconnect hub system is provided, the vehicle has a support coupled to the frame of the vehicle defining a bearing for the hub, and the wheel is mounted laterally outwardly on the vehicle from the support. Prior connect/disconnect hub systems usually are mounted laterally outwardly from the support and within the confines of the center of the wheel.
These prior devices generally have required units which extend laterally outwardly beyond the vehicle to house the operating mechanism necessary to provide the connect/disconnect feature. Since such must fit within the confines of the central portion of the wheel, they generally have had smaller diameter parts which rotate relative to each other in a disconnect position, and have splines or other interlock means which interconnect to lock them for driven operation. Due to part diameter limitations such prior devices have required substantially heavy elements to transmit the necessary torque to the wheel under driving conditions.
Further, such prior hubs have had laterally outwardly extending portions which may unsightly or produce other disadvantages.
In prior connect/disconnect hub units bearing sets provided between the support and the hub often have required specially designed bearings and supports due to the configurations of the hub units. Further, the axial dimensions of prior hub units have been such that often it has been difficult to obtain a desirable scrub radius, or steering offset. Furthermore, the scrub radius, or steering offset, may be defined as the distance between the point at which an extension of the king pin axis meets the road surface and the center of the area, or patch, of contact between the tire and the road. Zero offset, or scrub radius, occurs when the king pin axis line intersects the center of the area of contact between the tire and road surface. Positive offset occurs when the king pin axis line is spaced laterally relative to the vehicle from the center of the tire/road contact area. Negative offset occurs when the king pin axis line intersects the road laterally outwardly relative to the vehicle beyond the center of the tire/road contact area. Appropriate steering offset, or scrub radius, often has been difficult to obtain with prior devices.
A general object of the present invention is to provide a wheel end disconnect system including a clutch system which is adapted to provide driving engagement and disengagement (connect/disconnect) of a wheel to convert between driven and non-driven modes of wheel movement which overcomes the above-noted disadvantages of prior systems.
Yet another object of the present invention is to provide a novel clutch system in which the actuating mechanism to engage/disengage between driven and non-driven modes is mounted in a relatively protected region inwardly on the primary support and is simple and effective in its operation.
A still further object and advantage of the present invention is to provide a novel integrated wheel end unit which permits reduction of the scrub radius, or steering offset, to provide optimum driving performance.
More specifically an object of the present invention is to provide an inboard wheel end disconnect mounted to the tube yoke to connect the inboard side of the constant velocity joint to the axle shaft. The invention provides a system which includes clutch member shiftable between engaged and disengaged positions, whereby the clutch member is positioned laterally inside the constant velocity joint.
In accordance with one embodiment of the invention, a vehicle is provided with both 4xc3x972 and 4xc3x974 capabilities and, when 4xc3x974 capability is required, a negative pressure is applied to a vacuum cavity thus causing a piston, shift fork and spline collar to move inboard. The spline collar is splined to the constant velocity joint and as it moves inboard it locks on the spline plate locking the wheelend to the axle shaft. The invention also provides a default 4xc3x974 embodiment, the spline collar is splined to the joint and as the piston fork and spline collar move inboard, they unlock the wheelend from the axle shaft.